Answer:
The height (in m) above the floor of the top and bottom of the smallest mirror in which he can see both the top of his head and his feet is;
1.835 m and 0.88 m.
Explanation:
Here we have the total height of the man as
1.76 + 0.15 = 1.91 m
The mirror is positioned such that the person can see both the top of his head and his feet
We have the eyes are 0.15 m below the top of the head, therefore by the law of reflection, the incident and reflected angle must be equal.
Hence, the light from the top of his head and then reflected to his eyes forms a isosceles triangle, with the base being the distance of the eye to the top of his head and the top of the triangle is on the mirror.
The height of the mirror is then
1.91 - 0.15/2 = 1.835 m
Similarly, the distance from the eye to the feet is 1.76, therefore, the base of the mirror is positioned at 1.76/2 or 0.88 m above the ground.
The efficiency of steam engine is 26.66 %.
<h3>What is Efficiency?</h3>
The efficiency is defined as the work done by the engine divided by the heat supplied.
Work done is the difference between the heat supplied and heat rejected.
So, efficiency η = (Qs -Qr) / Qs
Given is the heat supplied Qs = 225 Joules and heat rejected Qr =285 . then the work done is
W = 225 -225 = - 60 Joules
Efficiency η = 60/225 x 100%
η = 26.66 %
Thus, the efficiency of the steam engine is 26.66 %.
Learn more about efficiency.
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It passes through C the Electron Cloud
Answer:
8N/m
Explanation:
The elastic potential energy stored can be calculated using the equation:
elastic potential energy = 0.5 × spring constant × (extension)2
assuming it is not stretched beyond the limit of proportionality.
Then calculate using the values in the question:
100J = 0.5 × spring constant × 5²
200J = spring constant × 25
spring constant = 200J ÷ 25m²
spring constant = 8J/m²
spring constant = 8N/m
From the answers provided, I believe the possible answer would be the last option, silicon, oxygen, and one or more metals. Here's my reasoning: the most abundant mineral group found in the Earth's crust is the silicate group. The silicate materials contain both oxygen and silicon. Silicates are the most common minerals in the rock-formation process, and it has, in fact, been estimated that they make up 75 to 90 percent of the Earth's crust. From this piece of evidence, I can guess that the answer will possibly be D, silicon, oxygen, and one or more metals.
It should also be noted that the additional elements that combine with the silicon-oxygen tetrahedron are involved with the other elements commonly found in the Earth's crust and mantle. They are aluminum, calcium, iron, magnesium, potassium and sodium.
